Yes, you are correct. The DLNR person also confirmed this when I asked. You can't take/damage the rock.My interpretation of the Hawaiian regulations around zoanthids is this: there does not appear to be a law which specifically prohibits the take of Zoanthids. However, there is a law against the take and damage of live rock (HAR 13-95). The definition of "live rock" is "any natural hard substrate to which marine life is visibly attached or affixed."
If a zoanthid is attached to a substrate that substrate is by definition live rock. So you can't break off the rock with the zoas because that is damaging and taking the live rock. Potentially, peeling the zoas off wouldn't break the rule, but I'm not a lawyer.
https://dlnr.hawaii.gov/dar/fishing/fishing-regulations/marine-invertebrates/
The issue with collecting the nice green ones way that they were all on the rock and it was very difficult to get them off especially since I did not have a thin razor blade or anything like that.
But I did find another variety on a small dead scallop, so I took that. A couple grains of sand were also taken, but I think that's fine. They mostly just want the live rock and hard corals undamaged.
But yet their are tourists constantly being negligent and stepping on corals and nothing can really be done, and people who are careful and want to raise these animals in captivity are punished due to the rulings (which does make sense)